Angle Tower Research Articles

Experimental study on the aerodynamic characteristics of combined angle transmission tower subject to skew wind

The transmission towers served as crucial carriers in the process of power transmission. The combined angle transmission tower of dual-angle steel with cruciform section are relatively a novel type of angle tower, which is being more widely used in transmission lines. The studies on aerodynamic characteristics of combined angle tower in skewed wind are limited. In this paper, the wind tunnel tests are conducted to investigate the aerodynamic characteristics of the combined angle tower, and the high frequency force balance (HFFB) test is introduced to obtain the transverse and longitudinal forces on the tower using the direct force measurement (DFM) method. The drag coefficients and wind load-distribution factors of the combined angle tower are obtained from the wind tunnel tests, and the effects of interference and tower leg spacing on the wind loads of the tower legs are fully explored. It can be found that the aerodynamic coefficients and drag coefficients of the combined angle steel tower leg tend to decrease with the increase of interference members and it also decreases with the decrease of the tower leg spacing. The test wind load-distribution factors of the isolated leg are generally larger than those defined by seven typical codes (e.g., US, EU, Japanese, and Chinese codes) and significantly exceed the code-specified values under partial wind angles. The observations obtained from this study may provide helpful guidance on the wind-resistant design of this relatively novel type of combined angle tower.

Algorithm for Solving Trip‐Out Rate Due to Shielding Failure of Bent Transmission Line

Accurate assessment of lightning protection performance of extra high voltage transmission lines is important for transmission line design and different lightning protection. Based on the electro‐geometrical model, this paper introduces the angle influence factor, and presents an algorithm for shielding failure trip‐out rate of angle tower, and the existing algorithm is expanded. By establishing the three‐dimensional geometric model of the angle tower, the electrical geometric relations of conductors and ground wires on both sides are analyzed, respectively, and the projection area algorithm for shielding failure is modified. To further verify the application value of the calculation algorithm, the change of the shielding failure trip‐out rate of the typical angle tower with the bending angle of transmission line and the tower height in a 500 kV transmission line is analyzed. The analysis results show that the trip‐out rate of the outside corner is higher than that of the inside one, and with the increase of the angle and the height of the tower, the trip‐out rate shows an upward trend. When the tension tower height is 71.5 m and the angle increases from 0° to 80°, the outside shielding failure trip‐out rate increased by 10.9% and the inside decreased by 9.3%. Compared with the classical electro‐geometrical model calculation, the difference of trip‐out rate is 4.3% when the bending angle is 80°. When the tangent tower height is 70 m and the angle increases from 0° to 40°, the shielding failure trip‐out rate on the outside increased by 5.9% while the inside decreased by 6.2%. The research results provide a simple algorithm for solving bending transmission line and give some reference for lightning protection design of EHV transmission lines. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Influence of finite element structural modification on dynamic characteristics of transmission tower

Taking a 500kV dry type single circuit angle tower as the research object, the computational modal analysis of the established finite element calculation model is carried out. It is found that local vibration occurs at the bottom of the transmission tower. The weakness of the original structure lies in the intersection of the longest web, the deformation displacement of the joint is the largest, so the structure needs to be strengthened. There are two corresponding strengthening methods: Diamond reinforcement and positive cross reinforcement. Further analysis results show that the regular cross structure has a certain strengthening effect on the original structure.

Retrofitted built-up steel angle members for enhancing bearing capacity of latticed towers: Experiment

Many existing transmission or communication towers designed several decades ago have undergone nonreversible performance degradation, making it hardly meet the additional requirements from upgrades in wind load design codes and extra services of electricity and communication. Therefore, a new-type non-destructive reinforcement method was proposed to reduce the on-site operation of drilling and welding for improving the quality and efficiency of reinforcement. Six built-up steel angle members were tested under compression to examine the reinforcement performance. Subsequently, the cyclic loading test was conducted on a pair of steel angle tower sub-structures to investigate the reinforcement effect, and a simplified prediction method was finally established for calculating the buckling bearing capacity of those new-type retrofitted built-up steel angles. The results indicates that: no apparent difference exists in the initial stiffness for the built-up specimens compared to the unreinforced steel angles; retrofitting the steel angles by single-bolt clamps can guarantee a relatively reasonable reinforcement effect and is suggested for the reduced additional weight and higher construction efficiency; for the substructure test, the latticed substructure retrofitted by the proposed reinforcement method significantly improves the lateral stiffness, the non-deformability and energy dissipation capacity; moreover, an apparent pinching behavior exists in the hysteretic loops, and there is no obvious yield plateau in the skeleton curves; finally, the accuracy validation result indicates that the proposed theoretical model achieves a reasonable agreement with the test results. Accordingly, this study can provide valuable references for the design and application of the non-destructive upgrading project of steel angle towers.

Exposure level control of power frequency electric field near angle tower of 500kV transmission lines

The distortion of power frequency electric field in the roof space near the angle tower of EHV line is serious, which is an important factor to be considered in transmission line planning and design. This paper establishes a three-dimensional electric field simulation model near the angle tower of 500 kV transmission line and verifies the validity of the simulation by field measurement. Based on this, the factors affecting the spatial electric field level on the roof of the house near the angle tower are analysed. Finally the control distance of the house near the angle tower is calculated according to the electric field exposure limitation in Chinese standards. The results show that the electric field near the transmission line is distorted and elevated by the house, and the electric field level of the roof decreases with the increase of the distance between the house and the line, and decreases with the decrease of the height of the house and the angle of the line.

Progressive Collapse Analysis of Latticed Telecommunication Towers under Wind Loads

As the antenna-supporting structures, latticed telecommunication steel towers are considered as critical members of telecommunication infrastructures. It is necessary to perform progressive collapse analysis of lattice telecommunication towers under wind loads. The present study conducts a nonlinear dynamic analysis on 50 m high typical standard latticed telecommunication tripole tower and angle tower by alternative load path method. The finite element models for two towers subjected to design wind loads are developed by ABAQUS. The analysis results show that, for 50 m high standard tripole tower, the member failure in the first three tower sections from tower top would not trigger the collapse of the tower. From the fourth tower section to tower bottom, the member failure at certain wind direction may cause a collapse. For 50 m high standard angle tower, the single member failure in any tower section would not cause the collapse of the tower. A dynamic sensitivity index is proposed to identify the most unfavorable wind direction for tripole tower and angle tower. A progressive collapse fragile curve based on collapse probability of telecommunication tower under wind loads is proposed to assess the anticollapse performance of the towers.

Research for the Working Method of Live Replacing the L-type Insulator String on ±800kV DC Transmission Lines

It would be hard to be repaired in the case of a power outage if the ±800kV ultra high voltage DC (UHVDC) transmission line was put into operation, so live working is the guarantee for its security and stability. Insulator strings of duplex L-type are widely used in UHVDC small angle towers. In the meantime, the tower structure and the insulator strings’ arrangement type is different than the V-type. In order to ensure the security and stability of the transmission line, this paper presents a method of live replacing the duplex L-type insulators based on the actual parameter of the UHVDC L tower type and develops apparatus as a complementary supporting by mechanics analysis. In order to ensure the safety of working staff, the safe distance and combined gap of the hanging basket method are checked. Safety precautions are also proposed in the paper by the calculation of body surface field strength of the persons doing live working in the finite element method. It is shown by the field application that the live working task of replacing the L-type insulator strings can be accomplished successfully by the method put forward in this paper, which provides reference for the following live working on the UHV transmission line.

The Response Analysis of Angle Tower Line System by Broken Lines

The suddenly break makes the tension of tight lines rapid realease. The tower system will be subject to impact,but the design specification considers the break load only by static load.Beacuse of the angle between the sides of the transmission lines and the span changes, In order to solve this problem this paper uses the finite element program ANYSY/LS-DYNA to build tower and lines system model and analyse the dynamic response of corner tower system in role of lines breaking by the numerical simulation. The study has shown that the effect of the corner to the corer tower disconnected power respose can not be ignored.

Wind-Induced Responses of a Transmission Angle Tower in Coastal Areas

The dynamic response analysis of a transmission angle tower subjected to wind excitations is actively carried out in this study. The structural model is constructed based on finite element approach with the aiding of commercial package ANSYS. The equation of motion of the transmission tower-line system under wind excitations is established. The dynamic wind loading are applied on the tower-line system to examine the structural responses. The deformation and stresses distribution of the transmission angle tower are computed to explore the structural performance. The made observations indicate that the peak stresses of some members are large than the permitted yielding stresses of steel material.

The Influence of Base Pre-Tilting on the Dynamic Properties of Angle Towers

As a significant bearing tower that is widely adopted in the electric transmission line, the angle tower is frequently found over-tilting in the inspection and maintenance of transmission lines. On the basis of the massive universal finite element software ANSYS, this study establishes a three-dimensional steel frame for the commonly used 500kV angle tower in the Inner Mongolian area, and analyzes the dynamic properties of angle towers while setting the base pre-tilting. It also conducts model analyses for the towers with or without base pre-tilting respectively, compares the frequency and mode of vibration, and paves way for further study of the setting of base pre-tilting and vibration response analysis.

Damage Inspection and Assessment on a Transmission Angle Tower in Coastal Areas

The field inspection and safety assessment of a transmission angle tower are actively carried out in this study. The field measurement and inspection are firstly introduced and then the structural model is constructed based on finite element approach with the aiding of commercial package ANSYS. The equation of motion of the transmission tower-line system is established for numerical analysis. The gravity, base settlement and dynamic wind loading are applied on the tower to examine the structural responses. The deformation and stresses distribution of the transmission angle tower are computed to explore the damage reasons. The made observations indicate that the peak stresses of some members are large than the permitted yielding stresses of steel material. The damage event is induced by coupling loading effects

A Study on Bearing Characteristics of Horizontally-Loaded Short Piles in 750kV Transmission Line on Loess Foundation

For the angle tower foundation of 750kV transmission line, the overturning effect caused by wire tension is a control factor of tower foundation design. The pile foundation on loess was taken as a research object in this study, where two typical regions along 750kV Lanzhou - Tianshui - Baoji transmission line were selected to carry out the site full-size horizontal static load test. Through the arrangement of displacement sensors and earth pressure cells around piles, the load-displacement curve of pile lateral soil under horizontal loads was obtained as well as the distribution law of soil stress at different locations of the pile. Based on the "m" method, the soil stress at different locations of the pile was calculated. The results showed that the calculated results were well consistent with experimental results. This research work can provide a theoretical basis and design guidance for tower foundation selection and design optimization of 750kV transmission line.

New fieldwork at the Severan fort ofMyd(…)/Gheriat el-Garbia on thelimes Tripolitanus

AbstractThe most outstanding oasis fort of thelimes Tripolitanus, Myd(---)/Gheriat el-Garbia, saw the deployment of various military units between AD 198/201 and 275/80. Archaeological research in 2009/10 focussed on the fortifications, particularly the main and rear gates, the northern angle tower and interval towers 2 and 4 as well as the curtain wall at its south corner. The towers of theporta praetoriahave been reconstructed theoretically with three storeys, at an overall height ofc.12.5 m. Of the headquarters building two of the rear rooms, including the shrine, were excavated. A monumental inscription of a length ofc.9.0 m and corresponding architectural elements suggest the existence of agromabuilding. Completely unexpected by archaeologists as well as ancient historians and rather spectacular is a late Roman reoccupation of the military site: after a hiatus ofc.80+ years building activities were undertaken within the fort and repairs and the blocking of the main gate could be observed and probably attributed to the deployment of a unit oflimitaneibetween AD 360/80 (at the earliest) and 430/55. The reoccupied fort might be identified with the so far unknowncastra Madensia, where themilites munificeswere garrisoned (Notitia Dignitatum Occ.31, 30). Further evidence of occupation, possibly of a Libyan chieftain and his tribe, has been assigned to the second half of the fifth century, continuing thereafter until AD 540+.

Analytical Study on Wind-Induced Vibration and its Control of Transmission Towers in Mountainous Area

A method for analyzing wind-induced vibration and its control of transmission tower-line system in mountainous area is described. The method is applied to a real transmission line containing two self-supporting steel angle towers, 3 spans of conductors and ground lines together with insulators. Analyses are conducted for the out-of-plane wind direction, and the fluctuating wind load on tower-line system is simulated by harmony superposition method and davenport spectrum. The numerical results indicate that the wind-induced response and its control effect are mainly related to the stiffness of the towers, rather than the mounting height or the spans of the power lines. At the same time, viscoelastic dampers fixed on the main members can suppress the wind-induced displacement of the towers effectively.

Fortificiranje grada Cresa u 16. stoljeću

U radu se objavljuju podaci i pretpostavke o fazama izgradnje pojedinih kortina, kula i vrata creskih fortifikacija 16. stoljeća, kao i imena kamenara, klesara i graditelja aktivnih na tom zadatku u razdoblju između 1508. i 1610. godine, zapisana u Libri delle fabbricha delle mura koji se čuvaju u Državnom arhivu u Rijeci.

DEFENSE CONSTRUCTIONS OF FORT UMREVINSKY (Based on 2002–2004 Archaeological Excavations)

Fort Umrevinsky is an example of the type of military architecture that reflects the early Russian colonization of the Upper Ob. The fort was built during the initial period of the Russian Empire's annexation of southwestern Siberia. The results of archaeological excavations indicate that the defense constructions of the fort include the outer and the inner walls, a moat, an angle tower, a palisade, and a platform. Two construction periods have been determined, dating to the early 1700 s and to 1730–1734. The latter period is marked by the construction of the angle tower, accompanied by rituals indicated by the presence of a foundation burial and a coin. By the late 18th cent., the defense structures had fallen into ruin and the fort was subsequently used as a cemetery.

A new gate-tower type in Pannonia Inferior. The northern gate of Annamatia

Roman forts can several times be dated only on the basis of the ground-plans of their gate-towers.1 This observation is true in the case of the forts in the Pannonian provinces as well. Here the earlier hypothesis that most of the Pannonian earth-timber castella were built into stone only after the Marcomannic wars on the basis of the gate-towers (projecting in the ratio 1/3:2/3 from the face of the fort wall) was confirmed by archaeological evidence in several places.2 In this paper we publish an earlier unknown gate type from Annamatia (Pannonia Inferior, Baracs) which was uncovered in the years 2000–2001. The antique Annamatia lies on the Eastern Pannonian limes, south of Intercisa (Fig. 1). The first archaeological investigation of the area was begun only in 1999 with the support of the Pazmany Peter Catholic University and the Intercisa Museum.3 The antique literary sources only mention the fort (It. Ant. 245, 2, Tab. Peut. Seg. IV, Not. Dig. occ. XXXIII, 95, Geogr. Rav. 220, 2). The praetoria side of the fort is almost completely missing because the Danube has eroded its eastern part. During the excavations between 1999–2004 we uncovered the SW and the NW angle towers and the northern gate (Fig. 1–2), as well as a short section of the western and southern fort wall. The excavation of the principia has also begun in 2002.4 Garrisons: 1st c. ? 106–118/119 cohort I Lusitanorum (L 2001, 38, No.30) 118/119–180 cohort I Alpinorum eq. (L 2001, 27, No.1) 180–260 cohort milliaria Maurorum (L 2001, 38, No.33) equites promoti (Not. Dig. occ. XXXIII, 36)

Non-linear behaviour of lattice panel of angle towers

Lattice microwave towers and transmission towers are frequently made of angles bolted together directly or through gussets. Such towers are normally analysed to obtain design forces using the linear static methods, assuming the members to be subjected to only axial loads and the deformations to be small. The effects of the end restraints, eccentricity of connections and secondary bracings (redundants) on the strength of the compression members are usually accounted for in the codal recommendations by modifying the effective length of the members and thus the design compressive strength. Hence, forces in the redundants are not known from the analysis and their design is empirical. In this study, non-linear analysis of angle compression members and the single panel of angle planar as well as three-dimensional lattice frames, as in typical lattice towers, are carried out using MSC-NASTRAN software. Account is taken of member eccentricity, local deformation as well as rotational rigidity of joints, beam-column effects and material non-linearity. The analytical models are calibrated with test results. Using this calibrated model, parametric studies are carried out to evaluate the forces in the redundants. The results are compared with codal provisions and recommendations for the design of redundants are presented.

Observations on the defences of roman forts in North Africa

This article examines the evidence for the date of the extant defences of the legionary fortress at Lambaesis and the relationship of the gates at angle and interval towers to the defensive curtain. The dating of the porta praetoria on typological grounds is assessed in the light of other recent finds of gates of the same type elsewhere in the Empire. Analogies for the unusual towers of the portae principales and the angle towers are sought and an attempt is made to explain their form and function.

The use of wide-flange shapes in transmission towers

The members of self-supporting latticed electrical transmission towers customarily consist of rolled angle sections. Nowadays, with transmission voltages in the extra-high-voltage and ultra-high-voltage ranges, the leg members are required to carry very heavy loads, especially in the case of heavy angle and anchor towers. Results of a study carried out on wide-flange shapes, to investigate their suitability as alternative sections to welded and built-up angles, are presented. The world's first transmission tower that has wide-flange shapes for legs and arms, Ontario Hydro's 500-kV double circuit heavy angle dead end tower type V6H, is described.